diff --git a/bert_score/utils.py b/bert_score/utils.py
index 745a4ea..1df6ad0 100644
--- a/bert_score/utils.py
+++ b/bert_score/utils.py
@@ -104,9 +104,9 @@ def sent_encode(tokenizer, sent):
         return tokenizer.build_inputs_with_special_tokens([])
     elif isinstance(tokenizer, GPT2Tokenizer):
         # for RoBERTa and GPT-2
-        return tokenizer.encode(sent, add_special_tokens=True, add_prefix_space=True, max_length=tokenizer.max_len)
+        return tokenizer.encode(sent, add_special_tokens=True, add_prefix_space=True, max_length=tokenizer.max_len, truncation=True)
     else:
-        return tokenizer.encode(sent, add_special_tokens=True, max_length=tokenizer.max_len)
+        return tokenizer.encode(sent, add_special_tokens=True, max_length=tokenizer.max_len, truncation=True)
 
 
 def get_model(model_type, num_layers, all_layers=None):